This invention relates to a snowmobile suspension unit and more particularly to an improved suspension unit for the drive belt of a snowmobile.
As is well known, snowmobiles travel over a wide range of territories and it is not uncommon for them to encounter unexpected and abrupt changes in terrain. In order to permit good control and yet a relatively soft ride when travelling over relatively smooth surfaces, it is particularly desirable to provide a suspension system that affords a fairly large degree of suspension travel. However, due to the construction and general configuration of a snowmobile, this is not always possible. Because of the relatively large space taken up by the drive belt, it has been difficult to provide a suspension system that will afford such wide degrees of suspension travel with full control throughout the entire range of travel. Although it has been proposed to mount the suspension medium externally of the drive belt, such an arrangement not only unduly widens the body of the snowmobile but further places the suspension components in a location where they may be damaged. In addition, such outboard mounting of the suspension units requires the use of two units, one at each side of the snowmobile, so as to insure against uneven loadings; thus, increasing the cost of the assembly.
It has been proposed, therefore, to provide a suspension system that is positioned within the area circumscribed by the drive belt. When the suspension system is so located, however, it is extremely difficult to insure the desired degree of suspension travel without interference with the components. Furthermore, in order to permit such internal mounting of the suspension unit, it has been proposed to use torsional, mousetrap type of springs. This type of spring has several disadvantages in that is has a high degree of hysteresis and, furthermore, may severaly limit suspension travel.
The conventional type of snowmobile suspension frequently has the spring and/or shock absorber mounted at one end directly upon the vehicle body. As a result, all of the suspension loading is directly transmitted to the body and this requires a robust construction which adds to both weight and cost. Also, in order to establish a greater suspension travel, it is desirable to incoporate a progressive spring rate. However, with conventional snowmobile suspensions, it has been difficult, if not impossible, to incorporate an arrangement that provides a progressive spring rate without the use of high hysteresis springs.
It is, therefore, a principal object of this invention to provide an improved, compact suspension unit for a vehicle such as a snowmobile.
It is another object of the invention to provide a compact snowmobile suspension unit which may be positioned within the driving track and which yet affords a high degree of suspension travel with adequate control throughout the range of travel.
It is yet a further object of this invention to provide an improved suspension system for the rear portion of the driving track of a snowmobile or the like.
It is yet another object of this invention to provide a suspension system that reduces loading on the body.
It is yet a further object of the invention to provide a compact, lightweight suspension system that permits the use of low hysteresis spring and which still affords a possibility of having a progressive spring rate.